1. Field of the Invention
The present invention relates to a method and apparatus for converting a color space of an OSD (On Screen Display), and more particularly, to a method and apparatus in which the image of a received data broadcasting contents are converted to accord with the color space of an OSD to be displayed.
2. Description of the Related Art
An output image format of a digital broadcasting receiver can be represented by using various color spaces. In other words, the output image can be reproduced with intended colors by selecting a video to be displayed and the color space which defines respective components of colors of the OSD.
Generally, the color space of an output image of the digital broadcast receiver is realized by the color coordinate system such as RGB (R: red, G: green, B: blue) method, YCbCr (Y: brightness, Cb, Cr: chrominance) method or the like. The RGB method defines the color on the basis of color components, and the YCbCr method defines the color on the basis of luminance and chrominance representing the brightness of a color.
However, since the two color spaces as above are different color coordinate system, colors of an image realized on a screen may be viewed abnormal if the color coordinate system for an input image and the color coordinate system for an output image are different from each other. Therefore, if the two color coordinate system are different, it is necessary that the color coordinate system for an input image should be converted to accord with the color coordinate system for an output image.
In the case of a video, the above conversion can be made through a hardware at a chip level. In contrast, in the case of OSD, the color space can be selected. However, the hardware only sets the color space of an image on OSD, but it does not convert the bitmap image on OSD automatically. In other words, in the case of OSD, the conversion can be possible according to the kinds of chips, but sometimes impossible.
Generally, contents for the digital data broadcasting are made to accord with the RGB color space, and therefore, a software for a browser for processing the contents is prepared under an assumption that the color space of the OSD is typically RGB. However, if the color space of the output image is set to be YCbCr, the RGB color space should be converted into the YCbCr color space.
Here, in the case of an OSD of 8 bpp (bit per pixel) or less, the property of an OSD color space is set by an indirect color display method using a palette. Here, the color space of an output image can be simply converted only by changing a palette in which color values are preset.
However, in the case of a direct color process of 16 bpp or more, since a bitmap image on an OSD represents color information, the bitmap image, itself, as well as the property of the OSD color space should be converted. That is, if the color coordinate system of an output image OSD is set to be a YCbCr color space of 16 bpp, and the color coordinate system of an input image is set to be an RGB color space of 16 bpp, an input RGB bitmap is recognized to be a YCbCr bitmap so that original colors are not realized fully enough, and the output image is realized as an image with different colors.